JP7713482B2 - Electricity storage device and method for manufacturing the same - Google Patents

Description

The present invention relates to a rectangular electricity storage device in which an electrode body is housed in a rectangular box-shaped case, and a method for manufacturing this electricity storage device.

Among prismatic batteries in which an electrode body is housed in a rectangular box-shaped case, batteries that are mounted on vehicles and used for long periods of time are generally externally restrained using restraining members outside the battery, which are made up of a pair of end plates and multiple restraining bands, for reasons such as improving charge/discharge cycle characteristics. This keeps the electrode laminated portion of the electrode body housed in the case in a state of being pressed in the thickness direction of the electrode body. For example, Patent Document 1 can be cited as a related prior art (see Figure 1 of Patent Document 1, etc.).

JP 2020-173893 A

However, using a restraining member to externally restrain the battery poses issues such as increased costs, larger size, increased weight, and an increased number of parts.

The present invention was made in consideration of this current situation, and provides an electricity storage device in which the electrode laminate of the electrode body is elastically compressed in the thickness direction of the electrode body by the electricity storage device itself, and a method for manufacturing the electricity storage device.

(1) One aspect of the present invention for solving the above problem is an electric storage device comprising a case and an electrode body housed in the case, the case being a rectangular box-shaped case having a rectangular first main wall portion, a rectangular second main wall portion facing the first main wall portion, and four rectangular side wall portions connecting the first main wall portion and the second main wall portion and extending in the case thickness direction, the electrode body including electrode plates and having a rectangular electrode stack portion in which the electrode plates are stacked in the electrode body thickness direction, the electrode body being housed in the case with the electrode body thickness direction parallel to the case thickness direction, the case being a bottomed square tubular main body member having the second main wall portion and the four side wall portions, and the first main wall portion and the four side wall portions. The device has a rectangular lid member having a wall portion and a lid peripheral portion joined to the opening peripheral portion of the opening of the main body member all around, and the electrode stack portion of the electrode body is elastically compressed in the thickness direction of the electrode body by the first main wall portion and the second main wall portion of the case, and the storage device is an electricity storage device having elastic characteristics such that, when the compression amount C of the electrode stack portion in a state in which the electrode body is housed in the case is C = c1 and the surface pressure P applied to the electrode stack portion is P = p1, in a graph showing the relationship between the compression amount C and the surface pressure P, with the compression amount C on the horizontal axis and the surface pressure P on the vertical axis, the slope of the tangent at point (c1, p1) is equal to or less than the slope (p1/c1) of the virtual line connecting the origin (0, 0) and (c1, p1).

In the above-mentioned electricity storage device, the first main wall and the second main wall of the case elastically compress the electrode laminate of the electrode body in the thickness direction of the electrode body. That is, this electricity storage device is a self-compressing type in which the electrode laminate of the electrode body is elastically compressed by the electricity storage device itself. For this reason, it is not necessary to use a separate restraining member when using the electricity storage device, or external restraint by a simple restraining member is sufficient.
Furthermore, in the above-mentioned energy storage device, the case is formed by joining a lid member forming the first main wall portion to a main body member forming the second main wall portion and four side wall portions, so that a self-compressing energy storage device can be easily manufactured as described below, and an inexpensive energy storage device can be produced.

Incidentally, there is variation in the thickness of the electrode laminated portion of each electrode body. For this reason, in a self-compression type electricity storage device, the compression amount C of the electrode laminated portion differs for each electricity storage device, and the surface pressure P applied to the electrode laminated portion also differs. If the surface pressure P applied to the electrode laminated portion varies greatly, the performance (such as charge/discharge cycle characteristics) of the electricity storage device also varies greatly.
In contrast, the above-mentioned electricity storage device has elastic properties in which the slope of the tangent at point (c1, p1) in the graph showing the relationship between the compression amount C of the electrode body and the surface pressure P is equal to or less than the slope (p1/c1) of the virtual line connecting the origin (0,0) and (c1, p1). That is, at point (c1, p1), the ratio (ΔP/ΔC: slope of the tangent) of the minute change ΔP in the surface pressure P caused by the minute change ΔC in the compression amount C is equal to or less than the slope p1/c1 of the virtual line. Therefore, in this electricity storage device, even if the compression amount C varies from one electricity storage device to another, the variation in the surface pressure P applied to the electrode stack can be reduced. Therefore, the variation in the performance (such as the charge/discharge cycle characteristics) of the electricity storage device can be reduced.

Examples of the "electricity storage device" include secondary batteries such as lithium ion secondary batteries, capacitors such as lithium ion capacitors, and all-solid-state batteries.
In addition, in the above-mentioned energy storage device, an intervening member made of metal or resin and consisting of a flat plate, a corrugated plate, or the like may be interposed between the first main wall portion of the case and the electrode laminate portion of the electrode body, or between the second main wall portion of the case and the electrode laminate portion of the electrode body.

(2) Yet another aspect is a case comprising an electrode body housed in the case, the case being shaped like a rectangular parallelepiped box and having a rectangular first main wall portion, a rectangular second main wall portion opposed to the first main wall portion, and four rectangular side walls connecting the first main wall portion and the second main wall portion and extending in the case thickness direction, the electrode body including electrode plates having a rectangular parallelepiped electrode laminate portion in which the electrode plates are laminated in the electrode body thickness direction, and the electrode body is housed in the case with the electrode body thickness direction parallel to the case thickness direction. the case has a bottomed rectangular tubular body member that forms the second main wall portion and the four side wall portions and has a rectangular opening formed by the four side wall portions, and a rectangular lid member that forms the first main wall portion and has a lid peripheral portion joined to an opening peripheral portion of the opening of the body member over an entire circumference, and the electrode laminate portion of the electrode body is elastically compressed in a thickness direction of the electrode body by the first main wall portion and the second main wall portion of the case, and the electric storage device is configured such that the electrode body is accommodated in the case. a graph showing the relationship between the amount of compression C and the surface pressure P, with the horizontal axis representing the amount of compression C and the vertical axis representing the surface pressure P, where C=c1 and P=p1 respectively of the amount of compression C of the electrode laminated portion in the state where the electrode laminated portion is in a compressed state, the gradient of a tangent at a point (c1, p1) being equal to or less than a gradient (p1/c1) of a virtual line connecting an origin (0, 0) and (c1, p1); the electrode stacking portion of the electrode body in the thickness direction of the electrode body by applying an external force to the first main wall portion formed by the cover member and the second main wall portion of the main body member; a joining process in which, while the electrode body is pressed and compressed, the cover peripheral portion of the cover member is joined to the opening peripheral portion of the opening of the main body member around the entire circumference to form the case; and a release process in which, after the joining process, the external force is released.

In conventional prismatic batteries, the case is made up of a bottomed rectangular cylindrical body member that forms the first and second main walls and three side walls of the case, and a lid member that forms one side wall. It is difficult to manufacture a self-compressing battery with this type of battery. This is because the gap between the first and second main walls of the body member is narrower than the thickness of the electrode body, or the combined thickness of the electrode body and the intervening member in a battery with the aforementioned intervening member, in order to press and compress the electrode body in the assembled battery, making it difficult to insert the electrode body, etc., into the body member.

In contrast, in the manufacturing method of the above-mentioned electricity storage device, in the housing step, the electrode body is first housed in a bottomed rectangular cylindrical main body member that forms a second main wall portion and four side wall portions, so that the electrode body can be easily housed in the main body member. Then, by carrying out the above-mentioned pressing compression step, joining step, and release step, it is possible to easily manufacture a self-compressing electricity storage device in which the electrode stacking portion of the electrode body is elastically compressed by the electricity storage device itself.

Note that examples of the method for joining the cover member to the body member in the "joining process" include joining by welding such as laser welding, and joining by crimping.

FIG. 1 is a perspective view of a battery according to an embodiment. FIG. 2 is an exploded perspective view of the battery according to the embodiment. 5 is a cross-sectional view taken along the line AA in FIG. 1 and FIG. 4, taken along the case width direction and case thickness direction of the battery according to the embodiment. FIG. 2 is a plan view of the battery according to the embodiment, seen from the inside in the thickness direction of a first main wall portion (second main wall portion) of the case. FIG. 2 is a perspective view of an electrode body according to the embodiment. 11 is a graph showing the relationship between the amount of compression C of the electrode body and the surface pressure P applied to the electrode body for a battery according to a comparative example and a battery according to an embodiment. 2 is a flowchart of a method for manufacturing a battery according to an embodiment. 11 is an explanatory diagram showing a state in which an electrode assembly is accommodated in a main body member in an accommodating step in a manufacturing method for a battery according to an embodiment. FIG. FIG. 11 is an explanatory diagram showing how an external force is applied to press the electrode body in the thickness direction of the electrode body in a press compression step in the manufacturing method for the battery according to the embodiment. 11 is an explanatory diagram showing how the lid peripheral portion of the lid member is laser-welded to the opening peripheral portion of the body member in a joining step in the manufacturing method for the battery according to the embodiment. FIG. FIG. 4 is a cross-sectional view of a battery according to a comparative embodiment, corresponding to FIG. 3 .

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a perspective view of a battery (electricity storage device) 1 according to this embodiment, FIG. 2 shows an exploded perspective view of the battery 1, and FIG. 3 shows a cross-sectional view of the battery 1. FIG. 4 shows a plan view of the battery 1 from the thickness direction inner side CH3 of the first main wall portion 11 (second main wall portion 12). FIG. 5 shows a perspective view of the electrode body 50. In the following, the case height direction AH, case width direction BH, case thickness direction CH, electrode body axial direction DH, electrode body width direction EH, and electrode body thickness direction FH are defined as the directions shown in FIGS. 1 to 5. The battery 1 is a rectangular (rectangular) sealed lithium ion secondary battery that is mounted on vehicles such as hybrid cars, plug-in hybrid cars, and electric cars.

The battery 1 is composed of a case 10, a flat wound electrode body 50 housed in the case 10, and a positive terminal 60 and a negative terminal 70 each supported by the case 10. Inside the case 10, the electrode body 50 is covered by a bag-shaped insulating holder (not shown) made of insulating film. Also housed within the case 10 is an electrolyte 3, a portion of which is impregnated into the electrode body 50 and the remainder of which is pooled on the second side wall portion 14, which is the lower wall portion of the case 10.

Of these, the case 10 is made of metal (aluminum in this embodiment). The case 10 is in the shape of a rectangular parallelepiped box, and has a first main wall portion 11, a second main wall portion 12, and four side walls portion 13 to 16 (a first side wall portion 13, a second side wall portion 14, a third side wall portion 15, and a fourth side wall portion 16), each of which has a rectangular shape.
The first main wall portion 11 and the second main wall portion 12 have a larger area than the side wall portions 13 to 16. The first main wall portion 11 and the second main wall portion 12 face each other, with the first main wall portion 11 located on one side CH1 in the case thickness direction CH (the front right side in FIGS. 1 and 2, and the upper side in FIG. 3), and the second main wall portion 12 located on the other side CH2 in the case thickness direction CH (the rear left side in FIGS. 1 and 2, and the lower side in FIG. 3).

On the other hand, the side walls 13 to 16 each extend in the case thickness direction CH, connecting the first main wall 11 and the second main wall 12. The first side wall 13 and the second side wall 14 face each other, with the first side wall 13 located on the upper side AH1 in the case height direction AH, and the second side wall 14 located on the lower side AH2 in the case height direction AH. The third side wall 15 and the fourth side wall 16 face each other, with the third side wall 15 located on one side BH1 in the case width direction BH, and the fourth side wall 16 located on the other side BH2 in the case width direction BH.

A safety valve 17 that ruptures and opens when the internal pressure of the case 10 exceeds a valve opening pressure is provided on the first side wall 13, which is also the upper wall of the case 10. The first side wall 13 is also provided with a liquid injection hole 13k that communicates between the inside and outside of the case 10, and is airtightly sealed with a disk-shaped sealing member 18 made of aluminum.
Furthermore, a positive electrode terminal 60 is fixed to the first side wall 13 near an end of one side BH1 in the case width direction BH. Specifically, the positive electrode terminal 60 is formed by crimping a plurality of metal members made of aluminum, and is fixed to the first side wall 13 in a state insulated from the first side wall 13 via a resin portion 65 made of a plurality of resin members. This positive electrode terminal 60 is connected to and conductively connected to the positive electrode current collecting portion 50c of the electrode body 50 inside the case 10, and also extends through the first side wall 13 to the outside of the battery.

A negative terminal 70 is fixed to the first side wall 13 near the end of the other side BH2 in the case width direction BH. Specifically, the negative terminal 70 is made by crimping multiple metal members made of copper, and is fixed to the first side wall 13 in a state insulated from the first side wall 13 via a resin portion 75 made of multiple resin members. This negative terminal 70 is connected to and conductively connected to the negative electrode current collecting portion 50d of the electrode body 50 inside the case 10, and also extends through the first side wall 13 to the outside of the battery.

The first main wall portion 11 of the case 10 has a pressing protrusion 11e having a rectangular shape in plan view in the central portion of the first main wall portion 11, excluding the peripheral portion 11s of the first main wall portion 11. This pressing protrusion 11e protrudes entirely toward the inner side CH3 in the thickness direction CH of the case (toward the electrode laminated portion 50e of the electrode body 50), and presses the electrode laminated portion 50e of the electrode body 50 in the electrode body thickness direction FH by elastic compression by the first main wall portion 11 and the second main wall portion 12 of the case 10.
The second main wall portion 12 of the case 10 has a pressing protrusion 12e having a rectangular shape in plan view in a central portion of the second main wall portion 12, excluding a peripheral portion 12s of the second main wall portion 12. The pressing protrusion 12e protrudes in its entirety toward the inner side CH3 in the thickness direction CH of the case (toward the electrode laminated portion 50e of the electrode body 50), and presses the electrode laminated portion 50e of the electrode body 50 in the electrode body thickness direction FH by elastic compression by the first main wall portion 11 and the second main wall portion 12 of the case 10.

The case 10 is composed of a main body member 21 in the shape of a rectangular cylinder with a bottom and a rectangular opening 21c, and a rectangular lid member 31. Of these, the main body member 21 forms the second main wall portion 12 and four side wall portions 13 to 16 described above, and the opening 21c of the main body member 21 is composed of the four side wall portions 13 to 16. On the other hand, the lid member 31 forms the first main wall portion 11 described above, and closes the opening 21c of the main body member 21. Specifically, the lid peripheral portion 31f of the lid member 31 is joined (welded) around the entire circumference to the opening peripheral portion 21f of the opening 21c of the main body member 21.

Next, the electrode body 50 will be described (see Figs. 1 to 3 and 5). The electrode body 50 is a rectangular parallelepiped part in which the positive electrode plate (electrode plate) 51 and the negative electrode plate (electrode plate) 54 are stacked on each other with a pair of separators 57 made of porous resin membranes in the shape of a strip, wound into a cylindrical shape around the winding axis DX, and then pressed into a flat shape. That is, the electrode body 50 has a pair of electrode R parts 50r located at both ends of the electrode body width direction EH, and an electrode laminated part 50e located between them. The electrode R part 50r is a semicylindrical part in which the positive electrode plate 51, the negative electrode plate 54, and the separator 57 are bent into a semicylindrical shape and overlapped. On the other hand, the electrode laminated part 50e is a rectangular parallelepiped part in which the positive electrode plate 51, the negative electrode plate 54, and the separator 57 are stacked in a flat shape in the electrode body thickness direction FH. Furthermore, the electrode body 50 has a positive electrode current collector 50c (described later) at an end on one side DH1 in the electrode body axial direction DH along the winding axis DX, and a negative electrode current collector 50d (described later) at an end on the other side DH2 in the electrode body axial direction DH.

The electrode body 50 is housed in the case 10 with the electrode body axial direction DH parallel to the case width direction BH, the electrode body width direction EH parallel to the case height direction AH, and the electrode body thickness direction FH parallel to the case thickness direction CH. The electrode body 50 is housed in the case 10 in a state compressed in the electrode body thickness direction FH (case thickness direction CH). In other words, the battery 1 is a self-compressing battery, in which the case 10 elastically deforms and the first main wall portion 11 and the second main wall portion 12 of the case 10 elastically compress the electrode laminate portion 50e of the electrode body 50 in the electrode body thickness direction FH.

The positive electrode plate 51 has a positive electrode current collector foil 52 made of a strip-shaped aluminum foil. On both main surfaces of the positive electrode current collector foil 52, a positive electrode active material layer 53 containing positive electrode active material particles capable of absorbing and releasing lithium ions is formed in a strip shape. At one end of the positive electrode plate 51 in the width direction, the positive electrode active material layer 53 is not present on the positive electrode current collector foil 52, and the positive electrode current collector foil 52 is exposed. In the electrode body 50, the exposed portion of the positive electrode current collector foil 52 protrudes in a spiral shape from the electrode laminated portion 50e to one side DH1 in the electrode body axial direction DH, forming the above-mentioned positive electrode current collector portion 50c. The positive electrode current collector portion 50c is connected to the positive electrode terminal 60.

The negative electrode plate 54 has a negative electrode current collector foil 55 made of a strip-shaped copper foil. On both main surfaces of the negative electrode current collector foil 55, a negative electrode active material layer 56 containing negative electrode active material particles capable of absorbing and releasing lithium ions is formed in a strip shape. At one end of the negative electrode plate 54 in the width direction, the negative electrode active material layer 56 is not present on the negative electrode current collector foil 55, and the negative electrode current collector foil 55 is exposed. The exposed portion of the negative electrode current collector foil 55 protrudes in a spiral shape from the electrode laminated portion 50e to the other side DH2 in the electrode body axial direction DH in the electrode body 50, forming the aforementioned negative electrode current collector portion 50d. The negative electrode current collector portion 50d is connected to the negative electrode terminal 70.

Here, the elastic properties of the battery 900 according to the comparative embodiment and the battery 1 according to the present embodiment will be described. First, the battery 900 according to the comparative embodiment will be described (see FIG. 11). This battery 900 has an electrode body 50 similar to that of the embodiment, but the shape of the case 910 is different from that of the case 10 of the embodiment. Specifically, the four side walls (first side wall (not shown), second side wall (not shown), third side wall 915, and fourth side wall 916) of the case 910 of the comparative embodiment are similar to the four side walls (first side wall 13, second side wall 14, third side wall 15, and fourth side wall 16) of the case 10 of the embodiment. On the other hand, the first main wall 911 of the case 910 of the comparative embodiment does not have a convex portion like the pressing convex portion 11e of the first embodiment and is flat. The second main wall 912 of the case 910 also does not have a convex portion like the pressing convex portion 12e of the first embodiment and is flat. This comparative battery 900 is also a self-compressing battery, in which the case 910 elastically deforms, and the first main wall 911 and the second main wall 912 of the case 910 elastically compress the electrode laminate 50e of the electrode body 50 in the thickness direction FH of the electrode body.

Next, the relationship between the amount of compression C of the electrode laminated portion 50e of the electrode body 50 and the surface pressure P applied to the electrode laminated portion 50e was investigated for each of the comparative battery 900 and the battery 1 of this embodiment. The results are shown in FIG. 6. The amount of compression C (mm) of the electrode laminated portion 50e of the electrode body 50 in a state in which the electrode body 50 is housed in the case 910 or case 10, i.e., in the completed battery 900 or battery 1, is C = c1, and the surface pressure P (MPa) applied to the electrode laminated portion 50e is P = p1.

The thickness of the electrode laminate 50e varies for each electrode body 50. Therefore, the compression amount C of the electrode laminate 50e differs for each battery 900, and the surface pressure P applied to the electrode laminate 50e also differs. In addition, the compression amount C of the electrode laminate 50e differs for each battery 1, and the surface pressure P applied to the electrode laminate 50e also differs. In both the comparative battery 900 and the battery 1 of the embodiment, the average value of the compression amount c1 is c1 = 1.0 mm, and the average value of the surface pressure p1 is p1 = 7.0 MPa.

First, in the comparative battery 900, as shown by the thick dashed line in graph GF2 in FIG. 6, the larger the compression amount C of the electrode laminate 50e, the larger the surface pressure P applied to the electrode laminate 50e. Specifically, as the compression amount C increases, the increase in the surface pressure P increases (the small change ΔP in the surface pressure P caused by the small change ΔC in the compression amount C increases). Therefore, in the comparative battery 900, the slope of the tangent TL2 at point (c1, p1) is larger than the slope (p1/c1) of the virtual line VL connecting the origin (0,0) and (c1, p1). In such a battery 900, if the compression amount C of the electrode laminate 50e varies for each battery 900, the surface pressure P applied to the electrode laminate 50e varies more. As a result, the variation in performance such as the charge/discharge cycle characteristics of the battery 900 also increases.

In contrast, in the battery 1 of this embodiment, as shown by the thick solid line graph GF1 in FIG. 6, the greater the compression amount C of the electrode laminate 50e, the greater the surface pressure P applied to the electrode laminate 50e. However, unlike the comparative embodiment, in this embodiment, the increase in surface pressure P decreases as the compression amount C increases (the small change ΔP in surface pressure P caused by the small change ΔC in compression amount C becomes smaller). Therefore, in the battery 1 of this embodiment, the slope of the tangent TL1 at point (c1, p1) is smaller than the slope (p1/c1) of the virtual straight line VL described above. In such a battery 1, even if the compression amount C of the electrode laminate 50e varies from battery 1 to battery 1, the variation in the surface pressure P applied to the electrode laminate 50e is small. Therefore, the variation in performance such as the charge/discharge cycle characteristics of the battery 1 is also small.

Thus, the battery 1 of this embodiment has elastic properties such that the slope of the tangent TL1 at point (c1, p1) in the graph GF1 showing the relationship between the compression amount C of the electrode laminate 50e and the surface pressure P is less than or equal to the slope (p1/c1) of the virtual line VL connecting the origin (0,0) and (c1, p1). The elastic properties of the battery 1 vary depending on the material and thickness of the case 10, the shape and size of the pressing protrusions 11e and 12e, the shape and size of the electrode body 50, etc., but it is difficult to predict the elastic properties when designing the battery 1. For this reason, in order to obtain a battery having the elastic properties according to the present invention, it is advisable to actually manufacture multiple sample batteries with different designs and investigate the relationship between the compression amount C of the electrode laminate 50e and the surface pressure P.

As described above, in the battery 1 of this embodiment, the first main wall portion 11 and the second main wall portion 12 of the case 10 elastically compress the electrode laminate portion 50e of the electrode body 50 in the electrode body thickness direction FH. That is, the battery 1 is a self-compressing type in which the battery 1 itself elastically compresses the electrode laminate portion 50e of the electrode body 50. For this reason, it is not necessary to use a separate restraining member when using the battery 1, or external restraint by a simple restraining member is sufficient.
Furthermore, since the battery 1 has a case 10 in which a lid member 31 forming the first main wall portion 11 is joined to a main body member 21 forming the second main wall portion 12 and the four side wall portions 13 to 16, the self-compressing battery 1 can be easily manufactured as described below, and the battery 1 can be made inexpensively.

Battery 1 also has elastic properties such that the slope of tangent TL1 at point (c1, p1) in graph GF1 showing the relationship between the compression amount C of electrode body 50 and surface pressure P is equal to or less than the slope of the virtual line (p1/c1). That is, at point (c1, p1), the ratio of the minute change ΔP in surface pressure P caused by the minute change ΔC in compression amount C (ΔP/ΔC: slope of tangent) is equal to or less than the slope p1/c1 of the virtual line. Therefore, even if the compression amount C varies from battery 1 to battery 1, the variation in the surface pressure P applied to electrode stack 50e can be reduced. This reduces the variation in performance, such as the charge/discharge cycle characteristics, of battery 1.

Next, a method for manufacturing the battery 1 will be described (see Figures 7 to 10). The body member 21 to which the positive electrode terminal 60 and negative electrode terminal 70 are fixed, and the cover member 31 are prepared in advance. The positive electrode plate 51, the negative electrode plate 54, and a pair of separators 57, each of which is in the shape of a strip, are wound into a cylindrical shape around the winding axis DX, and then pressed into a flat shape to form the electrode body 50. The electrode body 50 is then wrapped in a bag-shaped insulating holder (not shown).

Then, in the "accommodation step S1" (see FIG. 7), the electrode body 50 wrapped in an insulating holder is accommodated in the main body member 21 to which the positive terminal 60 and the negative terminal 70 are fixed (see FIG. 8). Specifically, the main body member 21 is placed on the flat mounting table 510 of the pressing device 500 with the entire second main wall portion 12 in contact with the mounting table 510. Then, the electrode body 50 is accommodated in the main body member 21 with the electrode body axial direction DH parallel to the case width direction BH, the electrode body width direction EH parallel to the case height direction AH, and the electrode body thickness direction FH parallel to the case thickness direction CH. Then, the positive electrode current collecting portion 50c of the electrode body 50 and the positive electrode terminal 60 fixed to the main body member 21 are connected by laser welding. Also, the negative electrode current collecting portion 50d of the electrode body 50 and the negative electrode terminal 70 fixed to the main body member 21 are connected by laser welding.

Next, in the "pressure compression step S2" (see FIG. 7), the lid member 31 is placed on the electrode body 50 housed in the main body member 21, and an external force Fa is applied to the first main wall portion 11 formed by the lid member 31 and the second main wall portion 12 of the main body member 21 to press and compress the electrode laminate portion 50e of the electrode body 50 in the electrode body thickness direction FH (see FIG. 9). Specifically, the pressing portion 520 of the pressing device 500 is brought into contact with the first main wall portion 11 formed by the lid member 31, and the lid member 31 and the main body member 21 are sandwiched between the pressing portion 520 and the mounting table 510, and an external force Fa is applied to the first main wall portion 11 and the second main wall portion 12. Then, the electrode laminate 50e of the electrode body 50 is pressed and compressed in the electrode body thickness direction FH, so that the lid peripheral portion 31f of the lid member 31 abuts against the opening peripheral portion 21f of the opening 21c of the main body member 21 along the entire circumference (see FIG. 10).

Next, in the "joining process S3" (see FIG. 7), the electrode body 50 is pressed and compressed by the pressing device 500, and the lid peripheral portion 31f of the lid member 31 is joined to the opening peripheral portion 21f of the main body member 21 over the entire circumference to form the case 10 (see FIG. 10). In this embodiment, the lid peripheral portion 31f and the opening peripheral portion 21f are irradiated with laser light LB to perform laser welding, thereby joining the lid peripheral portion 31f and the opening peripheral portion 21f over the entire circumference.

Next, in the "release step S4" (see FIG. 7), the external force Fa is released. That is, the pressing portion 520 of the pressing device 500 is moved away from the cover member 31 to release the external force Fa. At this time, since the case 10 has already been formed in the joining step S3, the compressed electrode body 50 does not return to its original state (thickness). After the external force Fa is released, the electrode laminate portion 50e of the electrode body 50 is elastically compressed by the first main wall portion 11 and the second main wall portion 12 of the case 10.

Next, in a "pouring and sealing step S5", the electrolyte 3 is poured into the case 10 through the pouring hole 13k, and the electrolyte 3 is impregnated into the electrode body 50. Thereafter, the pouring hole 13k is covered from the outside with a sealing member 18, and the sealing member 18 is laser welded to the case 10 to hermetically seal the space between the sealing member 18 and the case 10.
Next, in the "initial charging and aging step S6", a charging device (not shown) is connected to the battery 1 to perform an initial charge on the battery 1. After that, the initially charged battery 1 is left to stand for a predetermined time to age the battery 1. In this way, the battery 1 is completed.

Here, in a conventional prismatic battery, the case 10 is composed of a bottomed rectangular cylindrical body member that forms the first main wall portion 11, the second main wall portion 12, and three side walls (the second side wall portion 14, the third side wall portion 15, and the fourth side wall portion 16) of the case 10, and a lid member that forms the first side wall portion 13. It is difficult to manufacture a self-compressing battery with this type of battery. This is because the gap between the first main wall portion 11 and the second main wall portion 12 of the body member is narrower than the thickness of the electrode body 50 in order to press and compress the electrode body 50 in the assembled battery, making it difficult to insert the electrode body 50 into the body member.

In contrast, in the manufacturing method of the battery 1 described above, in the housing step S1, the electrode body 50 is housed in the bottomed rectangular cylindrical body member 21 that forms the second main wall portion 12 and the four side wall portions 13 to 16, so that the electrode body 50 can be easily housed in the body member 21. Then, by carrying out the pressing compression step S2, the joining step S3, and the release step S4, a self-compressing battery 1 in which the electrode laminate portion 50e of the electrode body 50 is elastically compressed by the battery 1 itself can be easily manufactured.

Although the present invention has been described above with reference to an embodiment, it goes without saying that the present invention is not limited to the embodiment and can be modified as appropriate without departing from the spirit of the present invention.
For example, in the embodiment, the flat wound type electrode body 50 is exemplified as the electrode body, but is not limited thereto. The electrode body may be, for example, a laminated type electrode body in which a plurality of rectangular positive electrode plates (electrode plates) and a plurality of rectangular negative electrode plates (electrode plates) are laminated with rectangular separators interposed therebetween.

1 Battery (energy storage device)
10 Case 11 First main wall portion 12 Second main wall portion 13 First side wall portion (upper wall portion)
14 Second side wall part (lower wall part)
15 Third side wall portion 16 Fourth side wall portion 21 Main body member 21c Opening 21f Opening periphery 31 Lid member 31f Lid periphery 50 Electrode body 50e Electrode laminate portion 51 Positive electrode plate (electrode plate)
54 Negative electrode plate (electrode plate)
57 Separator CH Case thickness direction FH Electrode body thickness direction C Compression amount c1 (of electrode laminate portion of electrode body) Compression amount P (of electrode laminate portion in battery) Surface pressure p1 (applied to electrode laminate portion of electrode body) Surface pressure GF1 (applied to electrode laminate portion in battery) Graph TL1 (related to battery of embodiment) Tangent line VL (related to battery of embodiment) Virtual straight line Fa External force S1 Accommodation process S2 Pressing compression process S3 Bonding process S4 Release process

Claims (2)

Case and
An electrode assembly housed in the case,
The case has a rectangular box shape, and includes a rectangular first main wall portion, a rectangular second main wall portion opposed to the first main wall portion, and four rectangular side wall portions connecting the first main wall portion and the second main wall portion and extending in a thickness direction of the case,
The electrode body includes electrode plates, and has a rectangular parallelepiped electrode laminated portion in which the electrode plates are laminated in a thickness direction of the electrode body, and the electrode body is housed in the case with the thickness direction of the electrode body parallel to the thickness direction of the case.
The above case is
a main body member having a rectangular opening formed by the four side walls and a bottomed rectangular tubular shape, the main body member forming the second main wall portion and the four side walls;
a rectangular cover member that forms the first main wall portion and has a cover peripheral portion joined to an opening peripheral portion of the opening of the main body member over an entire periphery,
the first main wall portion and the second main wall portion of the case elastically compress the electrode laminate portion of the electrode body in a thickness direction of the electrode body,
The electricity storage device is
When the electrode body is housed in the case, the compression amount C of the electrode laminated portion is C=c1, and the surface pressure P applied to the electrode laminated portion is P=p1.
In a graph showing the relationship between the compression amount C and the surface pressure P, with the horizontal axis representing the compression amount C and the vertical axis representing the surface pressure P, the energy storage device has elastic characteristics such that the slope of the tangent at point (c1, p1) is less than the slope (p1/c1) of a virtual line connecting the origin (0, 0) and (c1, p1). Case and
An electrode assembly housed in the case,
The case has a rectangular box shape, and includes a rectangular first main wall portion, a rectangular second main wall portion opposed to the first main wall portion, and four rectangular side wall portions connecting the first main wall portion and the second main wall portion and extending in a thickness direction of the case,
The electrode body includes electrode plates, has a rectangular parallelepiped electrode laminated portion in which the electrode plates are laminated in the thickness direction of the electrode body, and is accommodated in the case with the thickness direction of the electrode body parallel to the thickness direction of the case.
An electricity storage device,
The above case is
a main body member having a rectangular opening formed by the four side walls and a bottomed rectangular tubular shape, the main body member forming the second main wall portion and the four side walls;
a rectangular cover member that forms the first main wall portion and has a cover peripheral portion joined to an opening peripheral portion of the opening of the main body member over an entire periphery,
the first main wall portion and the second main wall portion of the case elastically compress the electrode laminate portion of the electrode body in a thickness direction of the electrode body,
The electricity storage device is
When the electrode body is housed in the case, the compression amount C of the electrode laminated portion is C=c1, and the surface pressure P applied to the electrode laminated portion is P=p1.
A method for manufacturing an electricity storage device having elastic properties such that in a graph showing a relationship between the compression amount C and the surface pressure P, with the horizontal axis representing the compression amount C and the vertical axis representing the surface pressure P, a gradient of a tangent at a point (c1, p1) is equal to or smaller than a gradient (p1/c1) of a virtual line connecting an origin (0, 0) and (c1, p1),
a housing step of housing the electrode body in the main body member;
a pressing and compressing step of disposing the lid member on the electrode body accommodated in the main body member, and applying an external force to the first main wall portion formed by the lid member and the second main wall portion of the main body member to press and compress the electrode laminate portion of the electrode body in a thickness direction of the electrode body;
a joining step of joining the lid peripheral portion of the lid member to the opening peripheral portion of the opening of the main body member along the entire periphery thereof in a state in which the electrode body is pressed and compressed, thereby forming the case;
After the joining step, a releasing step of releasing the external force is provided.